Biological purificn. of sewage and industrial effluent - with vacuum removal of dissolved gas and bubbles before sedimentation

摘要

One of the stages involves the sepn. of gas from the waste water. The extn. of a large proportion of both gas bubblesand dissolved gas is enhanced by reducing the press. on the surface if the waste water to well below atmos., i.e., to less than 0.4 (pref. 0.3-0.1) bar. In the case of a biological purificn. process comprising oxygenation, e.g. with injected air, followed by a sedimentation stage, the gas removal stage is introduced between oxygenation and sedimentation. A further stage of flotation sepn. may be included between oxygenation and gas removal. Used in the treatment of sewage and industrial effluents, the method removes a high proportion of dissolved gas as well as gas bubbles which, alone, could be satisfactorily eliminated by mechanical agitation. The resulting, more efficient removal of gas leads to better clarification by subsequent sedimentation.